Gasoline is a liquid oil fraction which is volatile at the boiling point range of about 30-200° C. From a constituent aspect, gasoline is a mixture of hydrocarbons of 4-12 carbons (see nonpatent document 1). The United States which is the world's largest consumer of gasoline consumed about 380 million gallon/day in 2004 and its consumption amounts to 40% or more in the world's gasoline consumption (see nonpatent document 2). Other than in the United States, gasoline has a significantly large influence on the economy and energy strategy of each country. Gasoline is currently synthesized from oil and the future oil-depletion problem (energy security) is of a great concern. Further, prevalence of cars, a representation of civilization, is considered to be the major cause of global warming due to carbon-dioxide emissions as a result of mass consumption of fossil fuels, and it is required to reduce carbon-dioxide emissions. In order to cope with this situation, car manufacturers have been developing hybrid cars, FFV, fuel-cell cars, electric cars, etc., among which hybrid cars and FFV are already penetrated the market in spite of their rather high prices.
On the other hand, a technique of synthesizing gasoline from methanol using a zeolite catalyst developed by Mobil Corporation (MTG), a technique of synthesizing liquid fuels from synthetic gas (GTL) and the like are known as synthetic techniques for new type of fuels (see nonpatent documents 3-5). Methanol, a material of MTG, is currently synthesized mainly from natural gas, i.e. fossil resources. Synthetic gas as a material of GTL is obtained from natural gas and biomass, but a liquefied fuel is an alternative fuel for light oil and cannot be directly used for gasoline-powered cars.
Gas engine, 4-stroke engine, diesel engine, jet engine and so on are well known as an internal combustion engine, i.e., a machine to retrieve energy. The current situation and problematic issues are as follows. Ethanol, butanol, Methyl tert-butyl ether (MTBE), and Ethyl tert-butyl ether (ETBE) are known as gasoline additives in a 4-stroke engine (see nonpatent documents 6-10). When ethanol is added to gasoline, existing gasoline-powered cars are said to be free of influence when the amount of ethanol added is up to about 10%. Hence, gasoline containing 10% ethanol is sold as gasohol (E10) in the United States. In Brazil, commonly used gasoline already contains ethanol by 22-26%. Gasoline containing ethanol by 85% (E85) and fuels of 100% ethanol require specialized cars. Ethanol, however, has a lower calorific value compared to gasoline and it has been reported that fuel consumption of E10 and E85 is poorer than that of gasoline. Further, mixing of water causes fuel layers to separate in an ethanol-mixed gasoline, which is said to be a cause of the engine trouble. MTBE had been used worldwide in 1980's as a means of NOx control in the exhaust gas and as an octane booster which was a substitute for conventional tetraethyllead. MTBE, however, has been revealed in the United States to be a substance that pollutes groundwater and more and more states have come to prohibit the use of MTBE. Presumably, MTBE will be totally prohibited in the near future. ETBE is synthesized from ethanol and isobutylene and is currently prevailing mainly in Europe in both aspects of as a MTBE substitute and as a plant-origin fuel additive. However, isobutylene, one of the materials of ETBE, is derived from oil so that it is inadequate as a global warming countermeasures and the problems of ecological safety and production cost remains.
It is expected that the production volume of these new type cars and new fuels will increase in the future. On the other hand, the currently existing gasoline-powered cars will certainly remain in the market in the next 20 years or so. Accordingly, substitute fuels that match these existing gasoline-powered cars are desired to be developed.
On the other hand, a method using a hydroxyapatite catalyst, wherein the solid acid and basicity on the catalyst surface are controlled, is proposed as a method for synthesizing a high-octane fuel using ethanol as a material (see patent document 1). In this method, however, the molar ratio of phosphorus and calcium in the catalyst needs to be carefully adjusted. Hence, there was a problem of difficulty in preparing the catalyst. In addition, the produced fuel is poor in oxidative stability and forms a lot of gum.    [Patent document 1] WO99/38822    [Nonpatent document 1] Gasoline Blending Streams Test Plan, Submitted to the US EPA by The American Petroleum Institute Petroleum HPV Testing Group, AR201-13409A, 2001.    [Nonpatent document 2] Motor Fuels Understanding the Factors That Influence the Retail Price of Gasoline, the United States Government Accountability Office, GAO-05-525SP, May 2005.    [Nonpatent document 3] Meisel, L. S., McCullough, P. J., Lechthaler, H. C. and Weisz, B. P. Gasoline from methanol in one step. Chemtech 1976, February, 86-89.    [Nonpatent document 4] Maiden, J. C., The New Zealand Gas-to-Gasoline Project, Methane Conversion, Elsevier Science Publishers B. V., Amsterdam 1988, 1-16.    [Nonpatent document 5] Baker, G. B. and Clark, J. N. Synthesis Gas to Motor Fuel via Light Alkenes, Methane Conversion, Elsevier Science Publishers B. V., Amsterdam 1988, 497-501.    [Nonpatent document 6] Demirbas, A. Progress and recent trends in biofuels. Progress in Energy and Combustion Science, 2007, 33, 1-18.    [Nonpatent document 7] Ancillotti, F. and Fattore, V. Oxygenate fuels: Market expansion and catalytic aspect of synthesis. Fuel Processing Technology, 1998, 57, 163-194.    [Nonpatent document 8] Malca, J. and Freire, F. Renewability and life-cycle energy efficiency of bioethanol and bio-ethyl tertiary butyl ether (bioETBE): Assessing the implications of allocation. Energy, 2006, 31, 3362-3380.    [Nonpatent document 9] Snelling, J., Curtis, W. C. and Park, Y-K. Synthesis of higher carbon ethers from olefins and alcohols. I. Reactions with methanol. Fuel Processing Technology, 2003, 83, 219-234.    [Nonpatent document 10] Hamelinck, N. C., Faaij, P. C. A., Outlook for advanced biofuels. Energy Policy, 2006, 34, 3268-3283.
All patents, patent applications, documents, and articles cited herein are herein incorporated by reference in their entirety.